From: Godswill Oletu (oletu@inbox.lv)
Date: Sun Apr 22 2007 - 20:51:09 ART
Hi Suplepo,
Think of route advertisement and traffic flow as opposite in direction. From
your scenario, R1 will originate and advertise both routes into BGP and to
eg R2 & R3.
If the routes are not manipulated traffic from devices beyond R2 & R3 will
choose beween R2 & R3 to reach networks 1.1.1.1/32 & 2.2.2.2/32 on R1.
My guess is, the task is asking you to eliminate the choice inherent in the
above scenario. eg if you configure R2 to disallow it from advertising one
of the routes to devices beyond it; traffic from devices beyond R2 will have
to source that network from other means e.g from R3.
Likewise, filter the other route from R3 advertisements and you will be
closer to fulfilling the requirements for the task.
HTH
Godswill Oletu
CCIE #16464
----- Original Message -----
From: "Suplepo" <suplepo@yahoo.com>
To: <ccielab@groupstudy.com>
Sent: Sunday, April 22, 2007 12:21 PM
Subject: BGP path manipulation
> I'm working through a sample lab and have hit a snag.
>
> R1 Is advertising networks 1.1.1.1/32 and 2.2.2.2/32
> into BGP. Instructions state
>
> 1) Configure R3 so that it's the preferred path for
> traffic network 1.1.1.1/32
>
> 2) Configure R2 so that it's the preferred path for
> traffic to network 2.2.2.2/32
>
> I can easily do this with AS-path prepending or MED,
> but since both of these must be configured on the
> non-desireable path I'm stuck. Is there anything I can
> do on the desired inbound path (R3 for 1.1.1.1) to
> ensure it's the best path. Since R1 is advertising the
> routes to both R2 & R3 conditional advertisement from
> R3 and R2 will not work.
>
> This all has me thinking I looking at a mistake in the
> question, but thought I'd bounce it off the collective
> to make sure there's not another option.
>
> Topology below,
> iBGP peerings R1<->R2, R1<->R3, R3<->R2
> eBGP peerings R3<->R4, R2<->R4
>
> |
> AS1 | AS2
> |
> R3--------eBGP-----------R4
> |\ |
> | \ |
> | R1 |
> | / |
> | / |
> R2---------eBGP----------|
>
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This archive was generated by hypermail 2.1.4 : Tue May 01 2007 - 08:28:37 ART